Identification of protective covers for medical imaging devices

ABSTRACT

A protective cover for medical imaging devices of the type having a probe with an optical system at a distal end includes a sheath of plastic material formed to enclose at least a portion of the probe and a transparent head secured to the sheath at a distal end of the cover. The transparent head provides a transparent window at the distal end of the probe to allow light to enter the probe and be imaged in a normal manner. Indicia are formed on the transparent head and are imaged by the medical imaging device. The image is then analyzed to determine if the indicia as shown in the image correspond to a preselected pattern, which may be one of a group of patterns which provide indications concerning the nature of the cover. If a pattern is recognized, the information corresponding to that pattern can be provided to an operator; if no pattern is recognized or if the pattern corresponds to an improper cover for the particular imaging device, a warning can be provided to the operator or the device disabled. The protective cover can be disposed after use with a patient, and a new cover applied to enclose the portions of the probe that will contact another patient, thereby minimizing potential spread of infection.

This application claims the benefit of No. 60/128,151, filed Apr. 7,1999.

FIELD OF THE INVENTION

The present invention relates generally to medical imaging devices andmore particularly to protective covers for providing infection controlbarriers for such devices.

BACKGROUND OF THE INVENTION

Each time a medical instrument or device comes in direct contact with apatient there is a danger of cross-contamination between patients, frompatients to medical personnel, or vice versa. Therefore, medical devicesand instruments that come in direct contact with patients are thoroughlycleaned between uses. For many large, expensive, or complicated medicaldevices, which are difficult or impossible to clean using conventionalmethods, cross-contamination prevention is provided by the use of aprotective cover placed over the device or over a portion of the devicewhich will come in direct contact with a patient. A clean protectivecover is placed on the medical device before each use. Although suchprotective covers may be cleaned and re-used, typically such protectivecovers are intended for only a single use and are disposable. Disposableprotective covers for medical instruments or devices are typically madeof a flexible or semi-rigid plastic material which is generally shapedto fit over the medical instrument or device with which the cover isdesigned to be used. Examples of medical devices for which suchdisposable protective covers are regularly employed includelaryngoscopes, endoscopes, ultrasound probes, and transesophagealechocardiographic probes. One such device is shown in U.S. Pat. No.5,363,838. Examples of disposable covers for medical devices are shownin U.S. Pat. Nos. 4,757,381, 5,168,863, 5,201,908, 5,359,991, 5,363,843,5,406,939, and 5,743,849.

In recent years, advancements in video imaging technology have enabledthe development of video imaging medical devices and video imagingaccessories for existing medical devices. Examples of such medicalimaging devices include dental cameras, retinal cameras, laryngoscopecameras, endoscopes (ENT and upper/lower gastrointestinal), as well ascamera systems used for various other types of non-invasive endoscopicsurgery. Although the designs of these various medical imaging devicescan vary greatly, all such medical imaging devices share some basicdesign similarities. Generally, a medical imaging device will include aprobe portion which is placed within or in contact with a patient. Anoptical system is placed at the distal end of the probe portion. Thisoptical system may include a miniaturized video camera or simply a lenswhich is connected to a camera via an optical, e.g., fiber optic, cablerunning from the distal end of the probe to the proximal end thereof. Alight source may also be provided at the distal end of the probe via,e.g., a fiber optic cable running through the probe from the proximalend thereof. The proximal end of the medical imaging device probe isconnected to a mechanical structure, e.g., a handle, for positioning theprobe. Electrical or optical signals from the optical system mounted inthe distal end of the probe are provided via an electrical or opticalcable to a computer based imaging and/or analysis system. The electricalor optical signals are converted into a video image, which may bedisplayed to a user of the device, and other observers, on a systemmonitor or display. The video image may also be digitized and operatedupon by the computer imaging/analysis system for image enhancement anddetailed computer analysis of the image.

Since medical imaging devices, and particularly the probe portionsthereof, come in direct contact with patients and their bodily fluids,measures must be taken to prevent cross-contamination when such imagingdevices are used. Typically, the cost, complexity, and design of mostmedical imaging devices prevents them from being thoroughly cleaned in aconventional manner between each use. Therefore, protective infectioncontrol covers are typically used with such medical imaging devices.Such protective covers typically cover at least the probe portion of themedical imaging device, and may extend to cover other portions of thedevice as well.

Since medical imaging devices depend on good optical performance fortheir operation, it is important that any protective cover mounted overthe distal end of the imaging device probe be integrated into theoptical system mounted therein to assure good image quality andrepeatable accurate results. Integration of a protective cover into theoptical system used in the medical imaging device requires that theprotective cover have a shape and be made of a material which does notinterfere with the performance of the medical imaging device. Even aproperly designed protective cover can adversely affect systemperformance if the protective cover is not properly mounted on theimaging device. A protective cover which does not meet the exactingoptical specifications (shape and material) for a particular medicalimaging device, or is not properly mounted on the device, may lead to apoor visual image, or, in the case of a diagnostic device, an inaccurateresult.

Optical pattern detection and identification techniques are widely usedin various commercial areas. Such techniques are employed, for example,in bar code systems used for product identification. A UPC bar code isplaced on a product. A laser-based bar code reading device is used todetect and identify the bar code and, therefore, the product. A similaridentification technique is used for mail sorting, by identifying codedstrips on the front of envelopes.

Optical pattern detection and identification techniques are alsoemployed by devices which use video images to measure the dimensions ofphysical objects, such as molded plastic or machined metal parts. Suchvideo inspection systems are commonly used in metrology laboratories,and are built by a number of companies, including Mitutoyo, Brown &Sharpe, RAM Optical Systems, and others. Objects placed upon the workingareas of such systems are viewed with surface illumination, or withbackground (shadowgraph) illumination to show edge detail.

Optical pattern identification techniques are also used for readingprinted pages of material. More complex pattern identification systemsexist for recognizing hand-written signatures, retinal patterns, andfinger prints.

Known methods for identifying geometric patterns, including textcharacters, involve first digitizing an image which contains thecharacters or pattern to be identified. The digitized image is providedto a computer system running a pattern recognition program. Relativelysimple pattern recognition programs are used for recognizing basicpatterns, including text and simple geometric shapes (lines, circles,squares, etc.), within the digitized image. More complex patterns arerecognizable through more complex techniques, such as statistical,structural, or syntactic methods. Even more complex patterns can berecognized through the use of neural networks which can be trained toevaluate patterns and interpolate from them. Examples of optical patternrecognition systems and methods are shown in U.S. Pat. Nos. 4,603,976,4,809,342, and 5,627,895.

SUMMARY OF THE INVENTION

The present invention provides an automated system and method fordetermining whether a protective cover meeting required specificationsis properly mounted on a medical imaging device. The system and methodof the present invention employs the optical and imaging/analysissystems of the medical imaging device itself to determine if aprotective cover meeting required specifications is in place on thedevice, and that the protective cover is properly positioned on thedevice. Visual indicia are placed on a head of the protective cover inthe field of view of the medical imaging device optical system. Theseindicia are included in the video image formed by the optical system.The video image is digitized and analyzed by the medical imaging deviceimaging/analysis system using pattern recognition algorithms to detectand identify the indicia. The visual indicia may provide information onthe nature of the protective cover, e.g., its size, shape, composition,etc., and may be used as alignment marks for the cover. In accordancewith the present invention, the medical imaging device is disabled, or awarning signal is provided, if analysis of the indicia in the videoimage, or lack thereof, indicates that either a protective cover is notpresent, an incorrect protective cover is being used, or the protectivecover is not properly positioned on the device.

The present invention may be employed to provide for the automaticidentification of protective covers for medical, dental or veterinaryimaging devices. In such imaging devices a video image is created by avideo system having an optical system mounted in the distal end of aprobe which is placed within or in contact with a patient to beexamined. The video image is digitized and provided to a computer basedimaging/analysis system. The computer based imaging/analysis system runsimaging and analysis programs for enhancing, displaying, manipulating,and analyzing the video image data.

In order to prevent cross-contamination, a protective cover is placedover the probe of the imaging device to provide an infection controlbarrier. The protective cover includes a plastic sheath formed toenclose at least a portion of the probe. A transparent head is securedto the plastic sheath. In accordance with the present invention, aprotective cover for a medical imaging device includes visual elementsor indicia formed on the head of the cover. The visual indicia areformed on the protective cover in an area of the head thereof which liesin the field of view of the imaging device optical system when the coveris properly positioned on the imaging device probe. The protective covermay be manufactured from any suitable optically transparent material,such as glass or plastics, and may be formed by machining, stamping,thermoforming, casting, molding, or any other process. The visualindicia may be formed as part of the head of the cover through theinitial forming process, may be created from a different material addedduring the forming process, or may be applied after the forming processthrough printing, etching, plating, painting, or some other process. Thevisual indicia may be in the form of basic geometric shapes (one or morecircles, lines, points, polygons, etc.) or more complex outline shapes,may include one or more characters of text, including letters andnumbers and/or may include a series of geometric or text elementspresented with specific dimensional intervals. The indicia may beconventional machine readable characters such as bar codes. In any case,the indicia will preferably identify the protective cover by size, type,material, etc. The indicia may also be used as alignment markings and/orto provide system calibration data.

Since the indicia are provided on the protective cover in the field ofview of the medical imaging device optical system, the digitized videoimage provided to the device imaging/analysis system will include theindicia if the cover is properly mounted on the device over the deviceprobe. In accordance with the present invention, the digitized videoimage is processed by pattern recognition algorithms in programs runningon the imaging/analysis system computer to detect and identify indiciaappearing in the video image. Edge-detection algorithms may be used todetect the perimeters of indicia based on “brightness” and “darkness”data contained in the video image signal. Contrast enhancementalgorithms may be run against the digital image data to enable improvededge detection. The perimeter data is analyzed by pattern recognitionalgorithms to recognize specific features of the indicia, includinglines, curves, or polygons. Recognized indicia patterns are comparedwith stored indicia patterns to ascertain whether the detected indiciaare a valid match for the stored patterns.

If the indicia pattern recognized in the video image does not match anystored valid indicia pattern, the protective cover identification systemof the present invention will provide a warning to a user of the imagingdevice that an incorrect protective cover has been placed on the device.Alternatively, the identification system of the present invention willdisable operation of the imaging device unless a valid indicia patternis recognized. The identification system of the present invention mayalso provide a warning to a user of the imaging device if the correctindicia pattern does not appear in the proper location on the videoimage, thereby indicating that the protective cover is not properlypositioned on the imaging device. The recognized indicia may also beemployed by the imaging device imaging/analysis system for otherpurposes, such as setting focal distances, calibrating size or distancemeasurements, or zeroing contrast and brightness settings, dependingupon the data provided by the indicia.

The protective cover identification system and method of the presentinvention may be used in combination with any medical, dental, orveterinary imaging or diagnostic device. The present invention providesan automated system and method for assuring that a protective cover isin place on the imaging or diagnostic device, that the correctprotective cover is being used, and that the protective cover ispositioned and oriented correctly. Thus, the present invention providesan automated system and method for both ensuring that an infectioncontrol barrier is in place and for ensuring that the barrier that isused does not adversely affect operation of the imaging device withwhich it is employed.

Further objects, features, and advantages of the present invention willbe apparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary medical, dental orveterinary imaging and diagnostic device employing a protective coveridentification system in accordance with the present invention.

FIG. 2 is a cross-sectional view of an exemplary protective coveremployed in a protective cover identification system and method inaccordance with the present invention as taken generally along line 2—2of FIG. 1, showing exemplary visual elements or indicia formed in thehead of the cover.

FIG. 3 is a flow chart of a computer implemented calibration process forprotective cover recognition in accordance with the invention.

FIG. 4 is a flow chart of a computer implemented protective coverrecognition process in accordance with the invention.

FIG. 5 is a view of the head of an exemplary cover as in FIG. 2 showingexamples of features of the head of the cover that may be detected andscreened in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an automated system and method foridentifying protective covers used on medical imaging devices. Thepresent invention automatically determines that a protective cover is inplace, that the correct protective cover is used, and that theprotective cover is correctly positioned and oriented on the imagingdevice. The present invention may be employed in combination with anymedical, dental, or veterinary imaging and/or diagnostic deviceemploying optical or video imaging. Such devices include dental cameras,retinal cameras, laryngoscope cameras, endoscopes (ENT and upper/lowergastrointestinal), as well as camera systems used for various othertypes of non-invasive endoscopic surgery. To emphasize the fact that thepresent invention is generically applicable to a wide variety of suchimaging and diagnostic devices, the present invention will be describedwith reference to the schematic illustration of a generic medicalimaging device 10 of FIG. 1. Although different types of medical imagingand diagnostic devices vary greatly in the details of their design andconstruction, most such devices will include the basic componentsincluded in the exemplary generic medical imaging device 10.

The medical imaging device 10 includes an optical or visual sensingstructure, typically in the form of a probe 12 or the like. As usedherein, the probe is generally the portion of the medical imaging devicethat comes in contact with the patient, including non-invasive contactas with the skin and contact by insertion in body cavities and surgicalwounds. The probe 12 may be formed, for example, from a rigid,semirigid, or flexible tube. An optical system 14 is mounted at a distalend 16 of the probe 12. The optical system 14 typically includes one ormore lenses (not shown) having a field of view directed outward from thedistal end 16 of the probe 12. Alternatively, the field of view of theoptical system 14 may be at an angle with respect to the axis of theprobe 12, and thus may be directed outwardly from the side of the probe12. The lenses in the optical system 14 mounted in the probe 12 may beconnected directly to a miniaturized video camera which is also mountedin the probe 12 and forms part of the optical system 14. Alternatively,an optical image may be carried from the lens in the optical system 14at the distal end 16 of the probe 12 via, e.g., a fiber optic cable 18,to a video camera system 20 located at the proximal end of the probe 12.If the video camera is included as part of the optical system 14 mountedin the distal end 16 of the probe 12, the cable 18 may include one ormore wires for carrying an electrical video signal from the opticalsystem 14 to the proximal end 22 of the probe 12. Depending upon thenature of the imaging device 10, the device probe 12 may include otheruseful structures (not shown) such as a light source provided at thedistal end 16 of the probe via, e.g., a fiber optic cable runningthrough the probe from the proximal end 22 thereof.

The proximal end 22 of the probe 12 is connected to a base unit 24 ofthe imaging device. Base unit 24 includes a handle 26 or other structurefor mounting or supporting the imaging device 10 such that the distalend 16 of the probe 12 can be placed within or in contact with the bodyof a patient at a desired location and position. The camera system 20 isalso mounted in the base unit 24. The camera system 20 converts theoptical or electrical signal provided by the optical system 14 mountedin the distal end 16 of the probe 12 into an electrical video signalwhich is provided on a cable 28 to an imaging/analysis system 30. Asdescribed previously, the camera system 20, or a portion thereof, may bemounted within the probe 12 adjacent to or as a part of the opticalsystem 14 mounted in the distal end 16 of the probe 12.

The imaging/analysis system 30 is typically remotely located from therest of imaging device 10 so as to not interfere with use of the imagingdevice 10. The imaging/analysis system 30 is connected to the rest ofthe remotely located imaging device 10 via the connecting cable 28. Thevideo signal provided on the cable 28 to the imaging/analysis system 30may be analog or digital in nature. If the video signal provided to theimaging/analysis system 30 is analog, the video image signal may beprovided directly to a display 32, such as a video monitor, connected tothe imaging/analysis system 30. The imaging/analysis system 30 istypically implemented using a general or special purpose computerincluding conventional personal computers. Preferably, the video imagesignal is digital in nature, or is converted into a digital signalwithin the imaging/analysis system 30. The digitized video signal may beoperated upon by programs running within the imaging/analysis system 30to enhance the video image before it is displayed on the video display32. Programs running in the imaging/analysis system 30 may also be usedto manipulate and analyze other information contained in the digitizedvideo image. Such computerized analysis of the digitized video imagesignal may be used, for example, to automatically locate physicalstructures of interest within the video image or provide a numericalanalysis of information contained within the video image. The results ofthis computerized analysis of the digitized video image may be displayedon the display 32, either in conjunction with or separate from the videoimage itself.

In order to prevent cross-contamination between patients, or frompatients to medical personnel or vice-versa, it is important to ensurethat any portion of the imaging device 10 which comes in contact with orin close proximity to patients and their bodily fluids be thoroughlyclean. However, due to the complexity and expense of the imaging device10, it is often not practical or possible to thoroughly clean the devicebetween each use. Therefore, a protective cover 34 is placed overportions of the imaging system 10 which will come in contact withpatients and their bodily fluids to provide an infection control barrierfor the device. As illustrated in FIG. 1, the protective cover 34includes a plastic sheath (which may be flexible, rigid or semi-rigid)that is formed to fit over and enclose at least a portion of the probe12. A transparent head 37 is secured to the sheath 35 at the distal end38 of the cover. The sheath 35 of the protective cover 34 may beextended to also cover the base unit 24 of the imaging system 10, or aseparate protective cover may be placed over the base unit 24, toprovide a more complete infection control barrier. A more completeinfection control barrier may be required, for example, where theimaging device 10 is employed in surgical situations. An attachmentstructure or mechanism 36 may be provided on the base unit 24 forattaching the protective cover 34 over the probe 12 to the base unit 24.The exact nature and design of the attachment mechanism 36 will dependon the design of the imaging device 10 and probe 12 employed on theimaging device 10.

The protective cover 34 may be made of a variety of rigid, semi-rigid,or flexible materials. The protective cover 34 may be made of a materialwhich may be cleaned and reused, or may be made disposable after eachuse. Exemplary materials from which the protective cover 34 may bemanufactured include glass and plastic. The protective cover 34 may bemade of different materials along its length. However, the head 37 atthe distal end 38 of the protective cover 34, within the field of theview of the optical system 14, provides a transparent window or “lens”(typically, non-focussing) at the distal end of the probe and is made ofan optically transparent material. The head 37 may comprise a solidtransparent disk. The protective cover 34 may be made in various ways.For example, the cover 34 may be made as a single injected molded part(integrally formed head and sheath) or with an injected head 37 (lens)that is insert molded with an extruded tube as the protective sheath 35that will extend over the probe 12. The head (lens) portion 37 of thesingle injection molded part or the injected head (lens) portion 37 ofthe insert molded part is preferably made from optically clear,potentially sterilizable thermoplastic resins with inherent lowbirefringence. Two examples of resins that meet these requirements thatmay be used to make the head (lens) 37 of the cover arepolymethylmethacrylate (acrylic or PMMA) and polymethylpentane (PMP).The tooling cavities to mold the lens portion 37 are preferablysingle-point and diamond-turned, in order to provide excellent opticaltransparency. An extruded tubular portion which forms the sheath 35 ofthe insert molded part may be made from a sterilizable plastic resinthat may be thermally, ultrasonically or mechanically bonded to theinjection molded lens 37 of the cover. Examples of plastic resins whichmay be used to form the sheath 35 are low density polyethylene andethylene vinyl acetate. Typically, the sheath 35 is flexible and isformed to fit snugly on the probe. The cover may be formed to conform tothe probe as described in U.S. Pat. No. 5,743,849, incorporated hereinby reference. The fabrication of protective covers for imaging systems10 generally, including methods of manufacture and materials from whichthe covers may be manufactured, are well known to those skilled in theart.

In accordance with the present invention, visual elements or indicia areformed on a portion 40 of the head 37 at the distal end 38 of theprotective cover 34 within the field of view of the optical system 14 ofthe imaging device 10. A view of the head 37 at the distal end 38 of anexemplary protective cover 34 in accordance with the present invention,as viewed from the optical system 14 of an imaging device 10, ispresented in FIG. 2. As illustrated, the portion 40 of the head 37 ofthe protective cover 34 having the visual indicia formed thereonpreferably only extends over a small portion of the field of view of theoptical system 14. This will minimize any interference by the indiciawith objects of interest to be viewed by the imaging system 10. Ofcourse, the portion 40 of the head 37 of the cover 34 having visualindicia formed thereon may be larger or smaller than that illustrated.

The visual elements or indicia may be formed on the head 37 of theprotective cover 34 in a variety of ways. For example, the indicia maybe formed as part of the head of the protective cover 34 through theinitial forming process. Thus, the indicia may be formed as molded-infeatures (e.g., surface bosses or indentations) of the head of theprotective cover 34 which will provide image contrast when light isprojected through the head. Alternatively, the visual elements orindicia may be formed during the forming process of the protective cover34 by use of an additional material added (e.g., on the surface orembedded) during the forming process. The visual elements or indicia maybe applied to the head of the cover 34 after the process of forming thecover 34 is complete, such as through printing, etching, plating, orother processes. It is apparent that the visual elements or indiciaformed on the head 37 of the protective cover 34 may be formed in anymanner.

The visual elements or indicia formed on the protective cover 34 maytake a variety of forms. For example, one or more characters of text 42may be formed on the head of the protective cover 34. The text mayindicate the source of the cover, e.g., the manufacturer's trademark,and/or other information about the cover, such as its type, size, etc.The textual elements may also provide information on the material oroptical characteristics of the cover 34. The visual elements or indiciamay take the form of basic geometric shapes 44, such as one or morecircles, lines, points, polygons, etc., or more complex outline shapes.These simple or complex geometric shapes may also be used to indicatethe manufacturer, type, size, nature, or composition of the cover 34.The visual elements or indicia may also be formed as a series ofgeometric or text elements with specific dimensional intervals betweenthe elements, such as a UPC bar-type code or other machine readablecharacters. In such a case, information on the manufacturer, type, size,or other characteristics of the cover may be found in the text elementsor geometric shapes and/or the size or nature of the intervals betweenthe characters or shapes. In accordance with the present invention, thevisual elements or indicia formed on the head of the cover 34 may takeany form capable of conveying information.

In accordance with the present invention, the visual elements or indiciaformed on the head 37 of the cover 34 are formed on a portion 40 thereofwhich is positioned in the field of view of the optical system 14 of amedical imaging device 10. Thus, the visual elements or indicia formedon the head 37 of the protective cover 34 will appear in the video imageproduced by the optical and camera systems of the imaging device.Ambient light, or light from a specifically designed source, such aslight from a light source mounted in the probe 12 and reflecting off ofportions of the patient's body being viewed by the imaging device 10,will shine through the head 37 at the distal end 38 of the protectivecover 34 and will be picked up as areas of “brightness” by the imagingdevice optical system 14. The visual elements or indicia formed on thedistal end 38 of the protective cover 34 are designed to block orinterfere with light entering the distal end 16 of the probe 12 in theareas wherein they are located. Thus, the areas in the field of view ofthe optical system 14 wherein the visual elements or indicia are locatedwill show up typically as areas of “darkness” in the image picked up bythe optical system 14. The areas of brightness and darkness which arepicked up by the optical system 14 form the video image which isprovided in digital form to, or converted to a digital form by, theimaging/analysis system 30.

Although the video image may be manually analyzed by the operator, inaccordance with the present invention, the digitized video image ispreferably automatically analyzed to determine the existence of,position of, and information provided by the visual elements or indicia(generally, patterns) found within the video image which correspond tothe visual elements or indicia formed on the head of the protectivecover 34. This analysis is performed using algorithms implemented ascomputer programs running in the imaging/analysis system 30. The visualindicia analysis programs may include edge-detection algorithms whichare used to detect the perimeters of the indicia in the video imagebased on the data in the video signal. Conventional edge-detectionalgorithms known in the art may be employed to detect the perimeters ofthe indicia in the video signal. Such edge detection algorithms aredescribed in, e.g., E. Gose, et al., Pattern Recognition and ImageAnalysis (book), CRC Press, 1997; F. Kammoun et al., “Optimum EdgeDetection For Object-Background Picture,” Graphical Models and ImagingProcessing, 1994, pp. 25-28; and M. J. J. Wang, et al., “A New EdgeDetection Method Through Template Matching,” International Journal ofPattern Recognition and Artificial Intelligence, 1994, pp. 899-917. Suchconventional edge-detection processes generally require only that aweighted matrix multiplication be performed against data points in thedigitized video image array. To enable improved edge detection, thevisual indicia analysis programs may include contrast enhancementalgorithms. Contrast enhancement algorithms are particularly useful incases where the visual elements or indicia are formed as molded-infeatures of head of the cover 34, created by replication of adimensional feature, or are engraved or etched into the head 37 of thecover 34, or in other cases wherein the contrast levels of the visualelements or indicia may be relatively low. Such contrast enhancementalgorithms are described in, e.g., P. Meer, et al., “MultiresolutionAdaptive Image Smoothing,” Graphical Models and Image Processing, 1994,pp. 140-148; and T. P. Kaushal, “Visibly Better Edge Detection UsingObserved Image Contrasts,” Pattern Recognition Letters, 1994, pp.641-647.

Pattern recognition algorithms are used to recognize and interpret theperimeter data derived by the edge-detection algorithms. Conventionalpattern recognition algorithms may be employed for this purpose to“read” the text characters or geometric shapes found in the video image.Such pattern recognition algorithms are described in, e.g., B. Jahne, etal., Digital Image Processing—Concepts, Algorithms, and ScientificApplications (book), Springer-Verlag, 1991; J. C. Russ, The ImageProcessing Handbook, CRC Press, 1995; R. Cole, et al., “On the Detectionof Robust Curves,” Graphical Models and Image Processing, 1994, pp.189-204; U. Seeger, et al., “Fast Corner Detection in Gray-LevelImages,” Pattern Recognition Letters, 1994, pp. 669-675; B. Bhavnagri,“A Method For Representing Shape Based on an Equivalence Relation onPolygrams,” Pattern Recognition, 1994, pp. 247-260. Pattern Recognitionmay also be carried out as described in the foregoing U.S. Pat. Nos.4,603,976, 4,809,342, and 5,627,895, incorporated by reference. Therecognized characters and shapes are compared to visual indicia elementsstored in memory which correspond to and indicate protective covers 34which are known to be appropriate for use with the particular imagingdevice 10 to provide satisfactory infection control without affectingperformance of the device 10. If a match between the visual elementsrecognized in the video image and valid visual elements stored in memoryis not found, the imaging/analysis system of the present invention willdetermine that an appropriate protective cover is not in place on theimaging device 10.

In accordance with the present invention, the imaging/analysis system 30may be programmed to take various actions in response to thedetermination that an appropriate protective cover 34 is not in place onthe imaging system 10. If the analysis of the digitized video imageresults in a determination that no visual elements or indicia are foundin the video image, or that the visual elements or indicia found in thevideo image do not correspond to valid visual elements or indicia storedin memory (preselected patterns), a warning may be provided on thedisplay 32 to a user of the imaging device 10. Additionally, theimaging/analysis system 30 may disable the imaging device 10, to preventits use, in such a case. The system thus provides an indication ofwhether the pattern has been found in the image. If the proper patternis found, rather than being a warming or message, the indication may beabsence of a message or may be a command to allow imaging to proceed.

In accordance with the present invention, the imaging/analysis system 30may also be programmed to determine the location of visual elements orindicia (a preselected pattern) in the digitized video image, and tocompare the detected locations with valid locations for the visualelements or indicia stored in memory. If the visual elements or indiciafound in the digitized image are not found to be in a valid location,but are otherwise valid indicia, a warning may be provided on thedisplay 32 indicating that the protective cover 34 is not properlypositioned on the imaging device 10. The system may also compare theorientation of the pattern found in the image with a valid orientation,and provide an indication of whether the pattern is in the validorientation. In addition, the imaging/analysis system 30 may disable useof the imaging device 10 if the protective cover 34 is found to beimproperly positioned or oriented.

Information contained in the visual elements or indicia recognized inthe digitized video image also may be employed by the imaging/analysissystem 30 for calibration of the imaging device 10 or other purposes.For example, information contained in the recognized visual indiciaconcerning the optical characteristics of the protective cover 34 may beused by the imaging/analysis system 30 for setting the focal distance ofthe imaging device 10, calibrating size or distance measures, or zeroingcontrast and brightness settings.

For purposes of exemplification, a flow chart of a calibration processimplemented by the computer of the system 10 in accordance with theinvention is shown in FIG. 3. This process is carried out prior to theprotective cover recognition process and exemplifies the calibrationthat may be utilized with generally diffused ambient light. A simplifiedprocess may be utilized where a standard target light source andpositioning fixture are available.

With reference to FIG. 3, the calibration process begins at the commandof the operator at 50 and proceeds to acquire a camera image data streamat 51. The gain amplitude of the camera is checked at 52 to determine ifthe light level is above the imaging threshold. If the check at 52fails, a request for retargeting is issued at 54, and the systemproceeds back to acquire new camera image data at 51. If the gainamplitude is acceptable at 52, a check is made to determine if a fixedor variable focus camera is utilized at 56; if the camera is fixed focusand near field (macro) or wide angle, the program proceeds to adjust tomaximum contrast setting at 57; if a variable focus camera is utilized,the program adjusts to the minimum focal length at 58 and then proceedsto adjust to the maximum contrast setting at 57. The program thenproceeds at 60 to capture an image frame and store the data in anordered array and then apply a contrast enhancement filter to the data(e.g., a centered-weight matrix multiplication) at 61. The process thenproceeds to test at 62 for defocus background (grain size distribution),which, if passed, results in a message to the operator at 63 on thedisplay device to place the cover on the instrument and continue. If thetest at 62 is failed, the program proceeds to block 54 to requestretargeting and then continues as described above.

Once calibration has been completed, the system may then proceed on tothe protective cover recognition process, exemplified by the flow chartof FIG. 4, and illustrated with respect to an example of a protectivecover shown in FIG. 5 that illustrates various types of features thatmay be screened for identification significance in accordance with theinvention. With reference to the flow chart of FIG. 4, the coverrecognition process begins upon command of the operator at 70 to capturea new image frame and store the data in an ordered array. A contrastenhancement filter is then applied at 71, for example, a center-weightedmatrix multiplication, and the program proceeds to the block 72 tointegrate the features of high opacity and rank by size (total area).The program then proceeds at 73 to process the “n” largest features indescending order where “n” is a preselected number or a number selectedby the operator. For example, referring to the illustration of FIG. 5,there are five features of various size on the cover that would beimaged by the camera, each of which is then ranked according to the sizeor total area occupied by each such feature.

After the processing at 73, the program proceeds to 74 to apply edgedetection and edge enhancement filters (weighted matrix operations), andthen at 75 proceeds to scale to match the features included with thearea of standard fiducial marks. The program then proceeds at 76 tooverlay features and to rotate about centroids to achieve the beststatistical shape match, and then proceeds at 77 to apply a thinningalgorithm to minimize extraneous details and to extract shape vectors.Statistical analysis is performed at 79 to measure the correlationbetween the feature and the standard. A first possible result of theanalysis is that there is no match, in which case the program proceedsback to the block 74 to again apply edge detection, etc. If no matcheshave been obtained in “n” tries, where “n” is a number preselected orselected by the operator, a message is provided at 80 (e.g., an audiblewarning or a message on the video screen for the imaging device) thatthe cover is not present or an incorrect cover is in use, and a warningis issued for the operator. If the analysis at 79 indicates that a matchhas been obtained but more than one feature has been matched, a warning(indication) is issued at 82 that the cover is correct but may becontaminated or damaged. If the analysis at 79 indicates at match onfeature number 1 (the largest feature), the cover is determined to becorrect, and the program proceeds at 83 to compare the size, rotationalposition and edge quality with the standard. If it passes this test, theprogram proceeds to issue a message at 85 that the test has been passedand the operator should proceed with use of the device; if the test at83 is failed, the program provides a warning to the operator asindicated at 86 and may instruct the operator on corrective positioningof the cover. If the system determines that a proper cover is being usedand is properly positioned, the operator then proceeds to use theimaging device to take an image through the head of the cover of a bodystructure for examination of the body structure. After the examinationhas been completed, the operator then removes the cover from the probeand, generally, disposes of the cover. The protective covers of theinvention may be formed inexpensively of plastic materials, allowingeconomic disposal after use, thereby minimizing the likelihood ofcross-contamination of patients.

It is understood that this invention is not confined to the particularembodiments herein illustrated and described but embraces all such formsthereof as come within the scope of the following claims.

What is claimed is:
 1. A disposable protective cover for a medicalimaging device of the type having a probe with an optical system at adistal end of the probe that receives light that is imaged by themedical device, comprising: (a) a sheath of plastic material formed toenclose at least a portion of the probe of the medical imaging device;and (b) a transparent head secured to the sheath at a distal end of thecover, the transparent head formed to provide a transparent window atthe distal end of the probe when the cover is mounted on the probe, thetransparent head formed to optically transmit light therethrough to thedistal end of the probe, the transparent head having visual indiciathereon in a position that will be within the field of the medicalimaging device at its distal end; wherein the cover formed by the sheathand transparent head is formed to protect the enclosed portion of theprobe from contamination when a medical device with the cover attachedthereto is used in a medical procedure.
 2. The cover of claim 1 whereinthe indicia are selected from the group consisting of geometricpatterns, letters, numbers, and combinations thereof.
 3. The cover ofclaim 1 wherein the indicia include machine readable markings.
 4. Thecover of claim 3 wherein the machine readable markings are bar codecharacters.
 5. The cover of claim 1 wherein the transparent head isformed of plastic.
 6. The cover of claim 5 wherein the sheath and headare integrally formed together of the same plastic.
 7. The cover ofclaim 5 wherein the head is formed as a transparent circular disk ofplastic.
 8. The cover of claim 5 wherein the indicia are molded into theplastic forming the transparent head.
 9. The cover of claim 5 whereinthe indicia are printed on the surface of the transparent head.
 10. Thecover of claim 5 wherein the head is formed of a disk of solidtransparent plastic and the sheath is formed of a flexible plasticjoined thereto.
 11. Medical imaging apparatus comprising: (a) a medicalimaging device having a probe with an optical system at a distal end ofthe probe which receives light at the distal end and provides image datacorresponding to the image of the light received at the distal end ofthe probe; (b) a cover extending over at least a portion of the probecomprising a sheath of plastic material formed to enclose at least aportion of the probe of the medical imaging device, and a transparenthead secured to the sheath at a distal end of the cover, the transparenthead formed to provide a transparent window at the distal end of theprobe, the transparent head formed to optically transmit lighttherethrough to the distal end of the probe, the transparent head havingvisual indicia thereon in a position within the field of the medicalimaging device at its distal end; and (c) processing means receiving theimage data from the medical imaging device for analyzing the image dataand recognizing selected indicia in the image from the medical imagingdevice corresponding to indicia on the head of the probe.
 12. Themedical imaging apparatus of claim 11 wherein the medical imaging deviceis an endoscope.
 13. The medical imaging apparatus of claim 11 whereinthe indicia are selected from the group consisting of geometricpatterns, letters, numbers, and combinations thereof.
 14. The medicalimaging apparatus of claim 11 wherein the indicia include machinereadable markings.
 15. The medical imaging apparatus of claim 14 whereinthe machine readable markings are bar code characters.
 16. The medicalimaging apparatus of claim 11 wherein the transparent head is formed ofplastic.
 17. The medical imaging apparatus of claim 16 wherein thesheath and head are integrally formed together of the same plastic. 18.The medical imaging apparatus of claim 16 wherein the head is formed asa transparent circular disk of plastic.
 19. The medical imagingapparatus of claim 16 wherein the indicia are molded into the plasticforming the transparent head.
 20. The medical imaging apparatus of claim16 wherein the indicia are printed on the surface of the transparenthead.
 21. The medical imaging apparatus of claim 16 wherein the head isformed of a disk of solid transparent plastic and the sheath is formedof a flexible plastic joined thereto.
 22. A method of covering a medicalimaging device to protect against the spread of infection, the medicalimaging device of the type having a probe with an optical system at adistal end of the probe which receives light at the distal end toprovide data corresponding to an image of the light received at thedistal end, comprising: (a) applying a cover over the probe of themedical imaging device, the cover comprising a sheath of plasticmaterial formed to enclose at least a portion of the probe of themedical imaging device, and a transparent head secured to the sheath ata distal end of the cover, the transparent head formed to provide atransparent window at the distal end of the probe when the cover ismounted on the probe, the transparent head formed to optically transmitlight therethrough to the distal end of the probe, the transparent headhaving visual indicia thereon in a position within the field of themedical imaging device at its distal end; (b) taking an image with themedical imaging device of the head of the cover to provide image data;(c) analyzing the image data to determine if the image data includes apreselected pattern; and (d) providing an indication of whether thepattern has been found in the image.
 23. The method of claim 22 furtherincluding, before the step of applying a cover over the medical imagingdevice, the step of taking a calibration image with the medical imagingdevice to provide calibration image data, and wherein in the step ofanalyzing the image data corresponding to the image of the head of thecover, utilizing the calibration image data to calibrate the image datafrom the image of the head of the cover.
 24. The method of claim 22further including disabling the operation of the medical imaging deviceif the preselected pattern is not found in the image data correspondingto the image of the head of the cover.
 25. The method of claim 22further including taking an image with the medical imaging devicethrough the head of the cover of a body structure for examination of thebody structure, then removing the cover from the imaging device anddisposing of the cover.
 26. The method of claim 22 wherein thepreselected pattern is selected from the group of patterns consisting ofgeometric patterns, numbers, letters, machine readable graphics, andcombinations thereof.
 27. The method of claim 26 wherein the preselectedpattern is an indicator of information concerning characteristics of thecover, and including the further steps if the preselected pattern isrecognized of providing a message to an operator indicating thecharacteristics of the cover that correspond to the preselected pattern.28. The method of claim 22 wherein if the preselected pattern is found,determining the location of the pattern and comparing the location to avalid location, and providing an indication of whether the pattern is inthe valid location.
 29. The method of claim 22 wherein if thepreselected pattern is found, determining the orientation of the patternand comparing the orientation to a valid orientation, and providing anindication of whether the pattern is in the valid orientation.
 30. Themethod of claim 22 further including analyzing the image data todetermine if the image data includes more than one match to thepreselected pattern and providing an indication if more than one matchis found.